This invention relates generally to satellite communication systems and, in particular, to satellite communication systems that employ a constellation of satellites in combination with terrestrial user terminals.
Communication systems generally referred to as Wired Loop Plans (WLP) have been implemented or proposed for various regions of the earth to either provide a basic communication system or to augment already existing systems. However, WLP systems must be accurate in their planning, can experience long delays in the roll out of services due to obtaining rights of way and environmental considerations, have a high cost/subscriber ratio, are susceptible to outages due to natural disasters, theft, and political instabilities, and also have high up-front costs.
In an effort to avoid or minimize such problems Wireless Local Loop (WLL) terrestrial communication systems have been introduced, especially in developing countries. Wireless Local Loop systems avoid some of the problems inherent in WLP systems, but are still expensive to implement due to their typically smaller coverage areas and the need for many xe2x80x9ccellsxe2x80x9d or base stations to provide adequate coverage.
It would thus be desirable to provide a WLL communication system that overcomes the problems inherent in the WLP systems, while also overcoming the problems inherent in existing WLL systems.
Also, commercial and other users are increasingly implementing TCP/IP protocol networks in response to the wide spread use of the Internet. At the present time it appears likely that TCP/IP will not only remain prevalent, but will need to be operable over satellite networks. Several experiments over the ACTS (Advanced Communications Technology Satellite) have shown that the TCP/IP protocol limits throughput, and analysis has shown this to be caused by the TCP window size and the TCP xe2x80x9cSlow Startxe2x80x9d algorithm for File Transfer Protocol. There may be alternative protocols developed to efficiently transfer information using TCP/IP (especially for satellite use), however, the installed base of equipment being deployed worldwide for using the terrestrial version of TCP/IP is expected to be dominant for many years.
It would thus also be desirable to provide a satellite-based communication system that overcomes the problems inherent in the use of conventional TCP/IP and other network protocols in a satellite-based system.
It would be further desirable to provide an ability to permit one user terminal to call another user terminal located within some region that can be serviced by at least one satellite, and to handle the call so as to minimize an amount of satellite communications system involvement in the call. In addition, it is desirable to extend the range and location of the local regional virtual gateway service areas.
Reference can be had to U.S. Pat. No. 5,884,142, issued Mar. 16, 1999, entitled xe2x80x9cLOW EARTH ORBIT DISTRIBUTED GATEWAY COMMUNICATION SYSTEMxe2x80x9d, by Robert A. Wiedeman and Paul A. Monte, the disclosure of which is incorporated by reference herein in its entirety.
It is a first object of this invention to provide a satellite communications system having an ability to permit one user terminal to call another user terminal, within some region that can be serviced by at least one satellite, and to handle the call so as to minimize an amount of satellite communications system involvement in the call.
It is second object of this invention to provide an Enhanced Wireless Local Loop communications system that provides single hop connectivity between WLL terminals and a terrestrial communications system, via a satellite communications system.
It is a third object of this invention to provide an Enhanced Wireless Local Loop communications system that provides single hop connectivity between WLL terminals in a first WLL service regions and WLL terminals located in a second WLL service region, via a satellite communications system.
It is a further object of this invention to provide a Satellite WLL system having one or more WLL service regions that are located within a regional service area, and to provide a virtual gateway for autonomously handling communications traffic into and out of the regional service area, in cooperation with a satellite communications system.
It is another object of this invention to provide a satellite-based communication system for serving one or more localized network areas, such as one or more of a WLL service area, a WLP service area, and a Local Area Network (LAN) service area, and that permits both fixed and mobile terminals to be provided service.
It is another object of this invention to provide a satellite communications system having an ability to extend the range and location of local regional virtual gateway service areas.
And, it is yet another object of the invention to allow locations for virtual gateways which are not within the service area of a gateway service area or an adjacent gateway area.
The foregoing and other problems are overcome and the objects are realized by methods and apparatus in accordance with embodiments of this invention.
Disclosed herein is a method for operating a communication system, comprising steps of: (a) receiving a call for a user terminal at a satellite system gateway, the call originating from another user terminal; (b) examining a database to determine if the called user terminal is located within a coverage area of the satellite system gateway; and (c) if yes, formulating a paging message and transmitting the paging message to the called user terminal, the paging message being transmitted via at least one satellite. Upon the called user terminal responding to the page, the method further (d) establishes the call using satellite system resources, (e) designates one of the calling or called user terminals as a call manager for the duration of the call, and (f) makes a temporary assignment of satellite system resources to the call manager user terminal for use in managing the remainder of the call. The step of establishing the call includes a step of assigning at least an initial channel/circuit pair to each of the user terminals.
A call synopsis is transmitted from the call manager user terminal to the gateway at the completion of the call, and the gateway employs the call synopsis when transmitting billing-related information from the gateway to another gateway with which one or both of the user terminals has an affiliation. The another gateway could be a virtual gateway that serves a localized region within the service region of the gateway.
At the completion of the call the assigned satellite system resources are relinquished.
This invention is preferably practiced in the context of a Satellite Wireless Local Loop (SWLL) system that eliminates most of the problems inherent in WPL and WLL systems. The SWLL system in accordance with this invention is enabled to adapt itself to system growth without resorting to typically inaccurate subscriber prediction market studies, can be rapidly deployed once the satellite system is in place, has a very low cost/subscriber ratio, and has a relatively low investment for a group or community served by the SWLL system.
This invention teaches a communication system, and methods for operating the communication system, of a type that includes a satellite communication system segment comprised of at least one satellite that projects a plurality of beams on the surface of the earth. The satellite communication system segment further includes at least one terrestrial satellite gateway that is bidirectionally coupled to the at least one satellite and also to a terrestrial communications system. In the communication system one or more overlapping beams from one or more satellites at the surface of the earth define an area within which at least one Wireless Local Loop (WLL) service region is located. This area is also referred to herein as a regional service area (RSA). The communication system further includes a terrestrial communication segment comprised of at least one WLL base station capable of bidirectional communications with a plurality of WLL user terminals within the WLL service region. The terrestrial segment further includes a virtual gateway that is bidirectionally coupled to the WLL base station and to the at least one satellite. The virtual gateway is responsive to the terrestrial satellite gateway for temporarily assuming control of satellite system resources for bidirectionally coupling a communication to or from an individual one of the WLL user terminals into or out of the WLL service region.
The virtual gateway is further bidirectionally coupled to a transmitter used for transmitting at least one of paging and broadcast messages to one or more of the WLL user terminals. The paging and broadcast messages are received by the virtual gateway from the terrestrial satellite gateway via the at least one satellite.
Also disclosed are methods and apparatus for extending the effective service regions of gateways and virtual gateways through a gateway-to-gateway diversity technique, wherein gateways are interconnected for providing user terminal traffic and signalling information between themselves at call setup and during a call.